1. Field of Invention
A novel mixed metal oxide catalyst for the production of carboxylic acids through catalytic vapor phase partial oxidation of C2-C8 hydrocarbons, particularly alkanes such as ethane, propane and butane, and its use for one stage selective production of corresponding oxygenated product, such as acetic acid, acrylic acid and acrolein and methacrylic acid, at lower temperatures.
2. Description of Related Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains and are hereby incorporated by reference.
The two stage vapor phase oxidation of propylene for the production of acrylic acid is known to the art. However, there is no commercial process that exists based on propane oxidation to acrylic acid. The production of acrylic acid from propane would be more attractive because of the significant price difference between propane and propylene.
There are few references reported in the literature relating to the production of acrylic acid from propane. U.S. Pat. No. 5,198,580 discloses a process for partial oxidation of propane to yield acrylic acid, propylene, acrolein, acetic acid and carbon oxides by the reaction of propane in admixture with a molecular oxygen-containing gas in a reaction zone with a catalyst containing BibMocVvAaDdEcOx; where A is one or more of K, Na, Li, Cs and Tl; D is one or more of Fe, Ni, Co, Zn, Ce and La; E is one or more of W, Nb, Sb, Sn, P, Cu, Pb, B, Mg, Ca and Sr; values for a, d and e are from 0 to 10, b is from 0.1 to 10, c is from 0.1 to 20, v is from 0.1 to 10, c:b is from 2:1 to 30:1 and v:b is from 1:5 to 1 to 8. The acrylic acid yield achieved using the bismuth molybdate type of catalyst is 5.4% at 19% conversion of propane at a pressure of 20 psig and a temperature of 400xc2x0 C.
European patent EP 0 608 838 A2 to Takashi et al. discloses a method of producing an unsaturated carboxylic acid, mostly in the explosive regime of the propane, air and water mixture at 380xc2x0 C. in the presence of a catalyst containing a mixed metal oxide of MoVTeXO, wherein X is at least one element selected from bismuth, cerium, indium, tantalum, tungsten, titanium, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum and antimony, wherein the proportion of the respective essential components are based on the total amount of the essential components exclusive of oxygen and satisfy the following formulae: 0.25 less than VMo less than 0.98, 0.003 less than Vv less than 0.5, 0.003 less than Vx less than 0.5, wherein VMo, Vv, VTe and Vx are molar fractions of Mo, V, Te and X.
Recently, Takashi et al. disclosed in another JP Patent No. 10 45 643 (98 45 643-Feb. 1998), the formation of acrylic acid and acrolein in the presence of PaMobVcWdXeOn (X=Nb, Ta, Ti, Zr, Sb; if a=1 then b=1-18, c=0-4, d=0-4 and e=0.05-20) at 380xc2x0 C. achieving a yield 0.9% to acrolein and 3.5% to acrylic acid at 12% propane conversion.
The above-referenced catalysts disclosed in the literature result in low yields of acrylic acid at relatively high temperatures and produce propylene as one of the significant by-products. Propylene can be expensive to separate, especially in a recycling mode of operation.
Thus, none of the prior art discloses or suggests catalysts which provide for the selective production of acrylic acid and acrolein at low temperatures through a gas phase partial oxidation process of propane.
It would be desirable to provide a catalyst designed in such a way that a single catalyst selectively produces oxygenated products such as acrylic acid and acrolein from alkanes such as propane without the significant production of intermediates such as propylene.
It is an object of the invention to overcome the above-identified deficiencies.
It is also an object of the invention to provide an improved catalytic system for the catalytic oxidation of C2-C8 alkanes and alkenes to corresponding acids.
It is another object of the invention to provide an improved catalytic system for the catalytic oxidation of propane to acrylic acid.
It is a further object of the invention to provide an improved catalyst system for the single stage oxidation of propane to acrylic acid.
It is a still further object of the invention to provide methods of making and using the improved catalytic system.
The foregoing and other objects and advantages of the invention will be set forth in or be apparent from the following description.
The invention relates to an improved catalyst system for the oxidation of alkanes and alkenes, and particularly C2 to C8 alkanes and alkenes, and most particularly alkanes such as ethane, propane and butanes and methods of making and using the catalyst. According to one embodiment of the invention, propane is selectively oxidized with molecular oxygen to acrylic acid and acrolein in a gas phase reaction at temperatures of 150xc2x0 C. to 450xc2x0 C. and at pressures from 1-50 bar. This is achieved using a novel catalyst with a calcined composition of MoaVbGacPddNbeXf wherein:
X=at least one element selected from the group consisting of La, Te, Ge, Zn, Si, In and W;
a is 1;
b is 0.01 to 0.9;
c is  greater than 0 to 0.2;
d is 0.0000001 to 0.2;
e is  greater than 0 to 0.2; and
f is greater than 0 to 0.5.
The numerical values of a, b, c, d, e and f represent the relative gram-atom ratios of the elements Mo, V, Ga, Pd, Nb and X, respectively, in the catalyst. The elements are preferably present in combination with oxygen in the form of various oxides.
The improved catalyst system is preferably prepared by the procedures disclosed in the examples.
Furthermore, this invention also relates to a selective low temperature catalytic process for the production of acrylic acid or acrolein or both by the vapor phase oxidation of propane, preferably in the non-explosive regime.
Other objects as well as aspects, features and advantages of the present invention will become apparent from a study of the present specification, including the claims and specific examples.